Magnesium dichloride/alcohol adduct and use of particles of magnesium dichloride/alcohol adduct as carrier in the preparation of catalysts for olefin polymerization are well known in the art. The known processes for preparing particles of magnesium dichloride/alcohol adduct include spray drying process, spray cooling process, high-pressure extruding process, high-speed stirring process, etc.
For example, U.S. Pat. No. 4,421,674 discloses a spray drying process for preparing particles of magnesium dichloride/alcohol adduct, comprising preparing a solution of magnesium dichloride in ethanol, then spray drying said solution to obtain spheric particles of magnesium dichloride/alcohol adduct. The particles of magnesium dichloride/alcohol adduct prepared by this process have a relatively small particle size, with more than 90% of particles having a diameter between 5 and 10 μm. Because a solution is required, a great amount of ethanol is needed, and the energy consumption for spray drying is relatively high.
WO 8707620, WO 9311166, U.S. Pat. Nos. 5,100,849 and 6,020,279 all disclose a spray cooling process for preparing particles of magnesium dichloride/alcohol adduct, comprising spray cooling a melt of magnesium dichloride/alcohol adduct having a molar ratio of alcohol to magnesium of from 3 to 6, to obtain spheric particles of magnesium dichloride/alcohol adduct. The drawbacks of said process lie in the difficulty for controlling process conditions.
U.S. Pat. No. 4,469,648 discloses a high-pressure extruding process for making particles of magnesium dichloride/alcohol adduct, said process using kerosene, liquid paraffin, while oil etc. having a low viscosity as reaction medium, and comprising the steps of heating the reaction system to a temperature of 120-130° C. and holding for a period of time, charging high-purity nitrogen gas into the reactor so that the pressure in the reactor reaches 10-15 atm, then discharging the mixture of the melt of magnesium dichloride/alcohol adduct and the reaction medium, through an outlet pipe having a length of 3-10 m and a inner diameter of 1-2 mm, into a cooling medium, wherein the flow speed of the mixture in the pipe is about 4-7 m/s. The formed solid particles after cooling is collected, washed and dried to obtain the particles of magnesium dichloride/alcohol adduct. The process applies relatively high requirement s to the apparatus, and the morphology of the obtained particles of magnesium dichloride/alcohol adduct is not so good.
U.S. Pat. Nos. 4,399,054, 6,127,304 and 6,323,152 all disclose a high-speed stirring process for preparing particles of magnesium dichloride/alcohol adduct, comprising dispersing a molten magnesium dichloride/alcohol adduct in form of droplets into an inert medium with a certain viscosity by high-speed stirring, then discharging the mixture at a certain flow speed into a cooling medium, which is pre-cooled to a low temperature, under stirring to solidify the melt by cooling, thereby obtaining spheric particles of magnesium dichloride/alcohol adduct. This process is simple, but still suffers from relatively large particle size and broad particle size distribution.
Thus, it is still in need to provide a process for simply and readily preparing particles of magnesium dichloride/alcohol adduct, with the particle size distribution of the obtained particles of magnesium dichloride/alcohol adduct being narrow and the particle size being readily controlled.